This invention relates to livestock, and more particularly to a livestock feed, the preparation of a livestock feed, and the feeding of livestock to increase utilization of protein, lipid and starch by ruminants.
It is known to treat feed for ruminants to reduce the microbial degradation of fed protein in the rumen. Various prior art methods of treating feed to reduce the microbial degradation of proteins have included (1) chemical treatment with tannin, (2) chemical treatment with formaldehyde, (3) heat treatment, (4) addition of spent sulfite liquor, (5) pelleting with calcium lignosulfonate, and (6) heat treatment combined with a reducing sugar.
Chemical treatment of feed with tannin is disclosed in U.S. Pat. No. 3,507,662. This patent discloses a process for protecting proteinaceous animal feed from rumen degradation by treatment of the feed with water and tanning agents, forming a paste, and drying at a temperature not to exceed 80 degrees centigrade. Subsequent work by Driedger (1972) J. Anim. Sci, 34:465 showed that tannin could be added to feed prior to pelleting, eliminating the paste forming step, and still effectively protect the protein from rumen degradation. Driedger used 20 percent tannin on soybean meal. Tannins, however, are subject to irreversible oxidative condensation which can render the protein unavailable in the abomassum (Fergusson, 1974, page 453 in Digestion and Metabolism in the Ruminant, Univ. New England Publ. Unit, Armidale, New South Wales, Aust.), and are not widely commercially accepted for use in feed treatment to protect protein.
Chemical treatment of feed with formaldehyde is described in U.S. Pat. No. 3,619,200. This patent discloses a feed for ruminants composed of proteinaceous material protected from rumen degradation by chemical modification of the protein through treatment with formaldehyde. Formaldehyde reacts with amino groups at neutral pH to form methylol groups which further condenses to form methylene bridges. In the acid pH of the abomassum, this reaction reverses, rendering the protein available and liberating formaldehyde (Fergusson, 1975). Hemsley, 1973, Australian J. Biol. Sci. 26:960 reported optimum treatment to be 0.8 to 1.2 percent formaldehyde. Higher levels would over-protect the protein and reduce nitrogen retention. Crawford, 1984, J. Dairy Sci. 67:1945 reported that the optimum treatment level will vary depending on the rate of passage of the feed through the rumen. Since this is highly variable, it may be difficult to use formaldehyde effectively. Although formaldehyde is approved for use as a biocide in feeds in the United States by the Food & Drug Administration, it is not approved to treat feed for ruminants to reduce microbial degradation of fed protein, lipid or starch in the rumen.
Heat treatment of feed is shown in U.S. Pat. No. 3,695,891. Heating proteinaceous feeds reduces degradability by reducing protein solubility and by blocking sites of enzyme attack through chemical modification. The reaction, however, is sensitive, and too little heat will not provide protection while too much heat will render the protein undigestible in the lower digestive tract (Sherrod, 1964, J. Anim. Sci. 23:510, and Plegge, 1982, J. Anim. Sci. 55:395).
Addition of spent sulfite liquor to feed is shown in Larsen, U.S. Pat. No. 4,377,596. Larsen discloses a method of feeding high producing dairy cows with a feed containing spent sulfite liquor in an amount of 0.25-3.0 percent by weight of the feed to increase milk production. The feed and spent sulfite liquor of Larsen is merely mixed together in a blender without any additional processing prior to feeding dairy cows. Larsen speculated that the lignin present in the spent sulfite liquor operated to protect the proteins in the feed from being destroyed by microorganisms present in the cow's first three stomachs. Additionally, Larsen speculated that the wood sugars in spent sulfite liquor may assist in better digestion of the materials present in the grains and roughage commonly found in feeds. However, it has now been shown that the lignin present in the spent sulfite liquor does not operate to protect proteins from degradation by microbes in the rumen, and the wood sugars in spent sulfite liquor do not necessarily provide better digestion of feed materials.
Pelleting feed with calcium lignosulfonate is shown in Stern, Can. J. Anim. Sci. 64 (Suppl.): 27-28 (September 1984). Based on continuous rumen culture in vitro studies Stern concluded that pelleting soybean meal with calcium lignosulfonate has potential for protecting protein from microbial degradation in the rumen. However, it has been discovered that calcium lignosulfonate is not the active component in spent sulfite liquor that protects the protein, and in fact pelleting with calcium lignosulfonate per se results in no protein protection.
Heat treatment combined with a reducing sugar is described in U.S. Pat. Nos. 4,957,748 and 5,023,091. To increase the efficiency of utilizing protein in feed by ruminants, feed containing a protein and a reducing sugar are mixed in quantities suitable for the Maillard reaction. The mixture is heated at a temperature, pH and time sufficient to cause early Maillard reactions, but not advanced Maillard reactions. Preferably, the sugar is xylose obtained by mixing sulfite liquor with the feed.
In U.S. Pat. No. 5,789,001, a ruminally inert fat for a ruminant feed is made by applying reducing sugars to oilseed meats and heating to induce non-enzymatic browning. The process is controlled to ensure penetration of the reducing sugars into the interior of cracked oilseed meat prior to browning. The browning reaction renders the protein which surrounds the oil resistant to rumen bacterial degradation to thereby encapsulate the oil in a protective matrix.
The prior art methods described above may be economical under some circumstances, but it is important to achieve the maximum cost saving and the best utilization of protein such as by increasing the efficiency with which fed protein is used by the animal. The prior art feeds and methods fall short of these goals by, in some cases, providing protein which has reduced nutritional value in an effort to increase the amount of protein actually transferred from the rumen to the small intestine of ruminants or have other disadvantages.